What is a reference parameter? give an example header.

and what are guidelines for when an argument should be passed by reference, and when by value?

given the options, i would say your best bet is c. the modem supports up to 56 kbps, which is too low for video streaming. dial up modems use actual phone lines, which only can go up to 56 kbps as that's more than sufficient for traditional phone calls. this is also the reason why when a dial-up modem connects, you hear all those sounds. it's literally using the phone line to establish a connection.

answer; i believe that the above statement is (true);

answer: a, c

divide any of the y values by x values and you will always get 3 is the most simple way i can put it for you.